1. Field of the Invention
The exemplary embodiment(s) of the present invention relates to a field of voice/video communication. More specifically, the exemplary embodiment(s) of the present invention relates to voice/video conferencing without using a presence server.
2. Description of Related Art
Communication over the Internet gains more and more importance. With increasing transmission rates and a better availability of Internet access, the utilization of the Internet is no more restricted to transmitting texts only for quite some time. Real time communication systems like Internet telephony (Voice over IP, VOIP) or video conferencing are gaining more and more importance. In particular, VOIP is not only a matter of interest for companies anymore, but also for regular customers using these technologies at home.
As in the traditional telephone networks, two phases can be basically distinguished for VOIP: the set up of a call and the transmission of the voice data. For the set up of the call, it is necessary to find the communication participants in the Internet as well as the corresponding communications paths between the individual participants. The communication paths comprise the individual servers and nodes that are necessary for the communication.
FIG. 1 shows a traditional video conference system. The system includes a STUN server 11, a presence server 12, a caller 13 and a callee 14. The STUN server 11 implements Simple Traversal of User Datagram Protocol (UDP) Through Network Address Translators (NATs), enables the caller 13 and callee 14 behind a NAT (that is, clients behind a router) to discover the presence of a NAT, the type of NAT, and then to learn the address bindings (including IP addresses and port mappings) allocated by the NAT. When the caller 13 or callee 14 sends a request to the STUN server 11, the STUN server 11 examines the request's source IP address and port and copies them into a response that it sends back to the caller 13 or callee 14. The presence server 12 handles registration, storage, and retrieval of presence information. Presence describes the caller/callee's availability and willingness to communicate. The presence server 12 can signal whether the caller 13 and callee 14 are on- or offline and whether they are idle or available. During the call set up phase, the caller 13 must look up the callee's public IP address/port in the presence server 12.
However, since the presence server 12 is generally provided by an internet service provider, the video conference or VOIP devices must be tightly coupled with user's subscription to a specific ISP. This is disadvantageous for end users.